1. Field of Invention
The present invention relates to a lens barrel capable of correcting a blur occurring in a subject image, which is used in an optical apparatus such as a camera.
2. Description of Related Art
Blur correction systems in the related art include a system that moves a blur correction optical system in a direction substantially perpendicular to an optical axis with an actuator, such as a voice coil motor (VCM).
For instance, a blur correction device disclosed in Japanese Laid-Open Patent Publication No. 11-271833 comprises a locking device that holds a blur correction optical system at a specific position, that is, locks the blur correction optical system while it is not engaged in blur correcting operation.
FIGS. 6 and 7 show sectional view of part of a lens barrel having a blur correction device in the related art.
When performing blur correction, electric current is supplied to a coil 20 to move a blur correction lens L and control its position in two directions perpendicular to an optical axis O and also perpendicular to each other. The blur correction lens L needs to be kept at a fixed position while blur correction is not performed. However, a great deal of power will be consumed if power is always supplied to the coil 20 to keep the position of the blur correction lens L.
When image blur in an image plane is unlikely to occur and blur correction is not being performed, there is no need to move a lens holding frame 10. In this case, the lens holding frame 10 and the blur correction lens L are locked by moving a lock pin 70b in a direction of the optical axis O to be inserted into a hole 10b, as shown in FIG. 6.
With the lens barrel in the related art, the locking operation is executed when an optical axis OL of the blur correction lens L and the optical axis O of a photographic optical system have matched with each other. In addition, the internal diameter of the hole 10b is set larger than the outside diameter of the lock pin 70b so that the lock pin 70b is inserted in the hole 10b with a high degree of reliability.
After the lock pin 70b is inserted into the hole 10b, power supply to the coil 20 is cut off, and thus locking operation is completed.
FIG. 7 shows the lens barrel shown in FIG. 6, which is in a state where the lock pin 70b and the hole 10b are engaged with each other and power supply to the coil 20 has stopped.
The lens holding frame 10 falls in a direction of gravity (a direction of arrow G shown in FIG. 7) under its own weight upon stopping of power supply to the coil 20. The lens holding frame 10 will no longer fall after the lock pin 70b and the hole 10b come into contact with each other, as shown in FIG. 7.
However, if power supply to the coil 20 has stopped and the lens holding frame 10 has fallen by its own weight, the optical axis OL of the blur correction lens L shifts from the optical axis O of the photographic optical system so that they become eccentric. There is a problem in that the optical performance of the photographic optical system slightly deteriorates when the optical axis OL of the blur correction lens L and the optical axis O of the photographic optical system do not match with each other.